Refining of cottonseed oil



May 25, 1943. w. J. BLooMER ErAL 2,319,970

REE'INING OF COTTONSEED OIL Filed March 10, 1939 TTCR EY( Patented May25, 1943 t REFINING OF COTTONSEED OIL Ward J. Bloomer, Westfield, andWalter J. Zahniser, Bayonne, N. J., assignors to The Lummus Company, NewYork, N. Y., a corporation of Delaware Application March 10, 1939,Serial No. 260,972

6 Claims. (Cyl.A 5560-425) This invention relates to improvements inrefining fatty oils such as animal and vegetable oils, and, moreparticularly, to the refining of fatty acid containing glyceride oilssuch as cottonseed oil.

Our invention is adapted to the refining of variour types of fatty oilsof the animal and vegetable type such as soy bean, castor, corn, maize,lard and fish oils, by the removal of the fatty acid content thereof. Itis particularly suitable for refining a cottonseed oil which normallyhas a fatty acid content of around 1 to 2% and a gum and resin contentof approximately the same amount. It is the principal purpose of theinvention to treat such oils so that they may be t for humanconsumption, viz., free of gums, resins, coloring matter, andsubstantially neutral.

It has heretofore been proposed that the refining of cottonseed oil becarried out under very careful temperature control to assure aneffective neutralization and a rapid separation of the soap stock. Ithas been found by some that it was necessary to neutralize atan emulsionforming temperature to assure an effective neutralization and preventthe setting of the color bodies and to prevent the increase ofV the acidnumber, and then heating has been required to give an emulsion breakingtemperature so that the soap 'stock could be effectively removed fromthe oil.

Very elaborate heating controls have been suggested with very expensiveapparatus as the result.

f The best prior practice has found it extremely diicult, however, toobtain a suitable color oil without excessive caustic or bleachingtreatments aoth of which are expensive and both of which materially addto the operating losses. Even with the best of care and the mostexpensive of equipment, it has been impossible to reduce the refininglosses to substantially below 4% which is still excessive.

In the prior application of Giles et al., Ser. No.

200,928, filed April 8, 1938, entitled Refining 0f cottonseed OiLtherehas been disclosed a process for refining animal and vegetable oilswhich includes the steps of water washing, decolorizing and neutralizingof the oil usually followed by the subsequent steps of oil extraction ofthe clay and soap treatment. Such a process has been found to havesuperior results in comparison to heretofore well known processes, butwe have since found that certain improvements in operating conditions asgenerally set out therein will assure a superior product and a higheryield.

The principal object of our invention is to provide an inexpensive,rapid, commercial method of treating cottonseed oil to remove the gums,resins, coloring matter and fatty acid content so that it may berendered satisfactory for human consumption and' so that losses arereduced to a minimum.

A more specific object of our invention is t0 provide an improvedarrangement; of the Sequential steps of water washing and neutralizinga. slyceride oil such as cottonseed oil which can be carried out underuniform temperature conditions and with a minimum of mechanicalapparatus and with a comparatively Short total time interval.

Another specific object of the invention is to providev improvedneutralizing and soap stock separating Steps. in the refining ofcottonseed oil Y'whereby high thruput can be obtained Without criticaloperating conditions and so that slight variations in operatingconditions will not materially impair the results.

Further objects and advantages of the invention will appear from thefollowing disclosure of a preferred form of embodiment thereof taken inconnection with the attached drawing which is a dow diagram showing themanner in which the process is preferably carried out.

In accordance with the preferred form of embodiment of our invention, itis proposed to first remove the gums and resins from the crude oil. Thisis accomplished by intimately mixing or homogenizing as by the apparatusdescribed in Cornells U. S. Patent 2,042,880 of approximately one to twopercent of water with the initial crude. It is preferable to use a meansto accomplish a mixture which readily separates and the homogenizerreferred to is particularly satisfactory for such purpose. Thereafter,the sludge which consists of mucilaginous matters, gums, resins and somecolor bodies is separated out either by a centrifuge or by settling,this latter being facilitated by using a coagulant such as of the metalsalts type. This water washed oil has markedly superior qualities asrespects original crude and greatly facilitates the neutralizing stepsas not only does the oil have a lower acid number, but it issubstantially free of emulsifying material.

The preferred second step in the operation is to neutralize this waterwashed oil with the theoretical quantity of alkali, a slight excess from2-10% and preferably about 5% being used as a practical matter. Thealkali is preferably introduced as an aqueous solution or an alcoholsolution or a combination of the two, The concentration may range from 5to 50% and for most purposes, to 30% is found most eective. A relativelysmall excess appears adequate probably because there is no extraneousmatter for the alkali to react with. Furthermore, there is nosaponication of the oil itself. The neutralization is also preferablycarried out in an homogenizer or device which will permit intimatemixing in a short period of time, also preferably of the type describedin Cornell U. S. Patent No. 2,042,880. The use of a device of this kindpermits of the introduction of the alkali as a highly concentratedsolution without damage to the product, if this is desirable.

Because of this unique apparatus, we obtain an admixture of theneutralizing agent and oil of a type which has been impossible by priordevices heretofore known. The alkali and oil are blended and compoundedin an exceptionally intimate attenuated stream or film and under thedesired vacuum. The total treating time is not substantially in excessof a second and ordinarily is but a fraction of a second the nlm issubjected to a substantial centrifugal force. This force acts tocontinuously carry the mixed oil and soap particles off the rotatingdisc. The nlm is extremely thin, in the neighborhood of .005" thick andis preferably not allowed to become subdivided or to substantially flashor vaporize. The soap thus remains soft and can be continuously treated.No emulsion results from this treatment at temperatures below 140 F. andeven as low as 70 F.

As no emulsion is formed, the soap particles readily separate from theoil and we find that in one hour, approximately 90% of the sludge orsoap stock will separate out. In some cases, a coagulant such as sodiumsilicate, and/or aluminum hydroxide may be added in very small amountsto facilitate this action. The settling action can take place in asingle tank or series of tanks of the intermittent type or may beaccomplished in a continuous settling device as disclosed in the DorrCompany patents. It is preferable to centrifuge this settled oil toremove the' residual oil from the soap stock, so that a completelyneutral and soap free oil can be obtained promptly and in largequantities and with a minimum of centrifugal aparatus. Thereafter, theoil can be further treated with clay if a premium color is desired andthe soap stock will be salted out oracidied as desired. By the sequenceof steps outlined, only a small quantity of clay is necessary ascompared with preliminary decolorizing procedure as the alkalineutralizing agent has already acted on the color bodies to a limitedextent.

In accordance with the attached drawing, the l preferred processincludes the mixing of the crude oil at l0 with approximately 1% ofwater at Il controlled by suitable proportionating devices l2 and I2a,for example, as described in Cornell U. S. Patent No. 2,109,331. Theproperly proportioned oil-water mixture is then introduced into themixing device I3. The mixing device which is preferably of the typedescribed in Cornell Patent No. 2,042,880, and is preferably operatedunder a vacuumobtained by vacuum line I4, intimately mixes the oil andwater. The mixture is then removed by the pump |5 and discharged intothe centrifuge IB. This maybe of either the batch or continuous type,but is preferably of the continuous type with the sludge removed at Iland .the gum-free oil removed at I8. If desired, a settling tank may beused lto remove part of the sludge prior to centrifuging to reduce thenumber of centrifuges otherwise necessary.

This gum-free oil removed at I8 is particularly characterized by itsfreedom from gummy, resinous and mucilaginous material and its freedomfrom a tendency to emulsify. It is temporarily collected in surge tankI9 from which it is pumped through proportionating device 20 into mixingdevice 22. The theoretical amount of caustic alkali from line 2| isestablished by proportionating device 20a and is separately introducedinto the mixing device 22. This is preferably of the homogenizer typedisclosed in the Cornell Patent 2,042,880 which is the only apparatusnow known which will accomplish the neutralization without forming apermanent emulsion. It is, of course, understood that the theoreticalamount of caustic may include quantities of of that theoreticallynecessary to neutralize the fatty acids but due to the very intimateattenuation within the homogenizer 22 and the complete contact in theshort time, the theoretical amount of caustic is adequate to neutralizethe fatty acids and there is no saponiiication of the oil.

The homogenizer 22 is also preferably operated under a vacuum induced at24. The vacuum prevents oxidation and prevents entrainment of air andassists in maintaining the thin nlm which is so essential. Havingeliminated the emulsifying material and having operated under theVacuum, and with an attenuated and continuous stream in the homogenizer,the soap and oil mixture does not emulsify. It will readily separate andis preferably discharged by pump 23 into a settling tank 25. Suchmixture has no free caustic therein and the oil phase has a very lowacid content in the range of .03% or less.

Settling of this oil for an hour period and with a coagulant, ifdesired, will permit approximately 90% of the oil to becomesubstantially free of soap particles. To make the process continuous andto materially reduce the number of centrifuges required, the tank 25 isconveniently of two to three hours capacity which, at 1500 gallons perhour capacity of the homogenizer, is from 3000 to 5000 gallons. Such oilis then drawn oil" at the top and centrifuged or mechanically separatedat 21 to complete the freeing of the oil from the soap stock whichdischarges at 28. The oil is discharged at 29 to surge tank 3l, and inthis case is bright in color, free of gums and resins and is neutral.From time to time or continuously with a continuous type of settlingtank, soap stock is removed The oil is filtered from the clay in filter36 and thebleached oil discharges at 31. removed at 38.

.The temperatures of operation may be varied within considerable limits.If the entire proc- The clay is ess, including water washing,neutralizing, etc.,

is operated at 90 F., the loss of material as gums,

`resins and soap stock can be kept down to 3.9%

of the charge with a free fatty acid content n ot to exceed 2%. When theprocess is lcontmuously operated at F., the reiining loss in the waterWashing and neutralizing is reduced to around 2.9%, which is probablydue to the reduced viscosity of the oil at the higher temperature. Thethruput is also more rapid than at 90 F. Operating much above 140 F.does not appear to be helpful. The range of 125-145 F. appears to be thebeneficial limits of the operation.

Under normal conditions, no heat need be added at any stage although itwill probably be found advisable to insulate the apparatus to conservean initial temperature so that the conditions are as nearly constant aspossible.

While We have shown and described a preferred form of embodiment of theinvention, We are aware that modifications may be made thereto and Wetherefore, desire a broad interpretation of the invention within thescope and spirit of the invention as described herein and as claimedhereinafter.

We claim:

l. The method of refining cottonseed oil which comprises the steps ofmixing the cottonseed oil With a proportionate amount of Water such thatthe gums, resins and mucilaginous compounds are converted to oilinsoluble material, thereafter continuously removing said insolublematerial, blending said oil, free of said oil insoluble material, withsubstantially the theoretical amount of caustic alkali necessary toneutralize the free fatty acids in the oil, maintaining said oil andcaustic alkali mixture in a thin film, under a sub-atmospheric pressure,and under a substantial centrifugal force for a period not substantiallyin excess of a second, thereafter settling said oil and soap stock topartially remove the soap stock, and subsequently centrifugallyseparating the partially settled oil to completely remove the soapstock.

2. An improved method for continuously removing the gums and resins in acrude glyceride oil which comprises the steps of mixing the oil withapproximately 1% of Water, passing said mixed materials to a rotary diskmixing device,

rotating said disk at a relatively high peripheral speed to cause saidmaterials to flow across the disk in a continuous thin film undersubstantial centrifugal force, removing the thin film continuously andpassing it into a liquid receiving zone Without forming an emulsion ofthe oil, and continuously separating the oil and hydrated matter bycentrifugal force, the movement of the oil being continuous and confinedfrom the air.

3. An improved method for refining a glyceride oil as claimed in claim2, in which the oil is subsequently combined with a caustic neutralizingagent on a rotary disk mixing device which is yoperated at a relativelyhigh peripheral speed to cause said materials to flow across the disk ina thin lm under substantial centrifugal force for the immediateneutralization of the fatty acids therein, and the oil is removed in acontinuous film into a liquid receiving zone Without forming an emulsionof the oil.

4. In the refining of cottonseed oil the improvement which comprises thesteps of conducting separate streams of oil and a caustic neutralizingagent to a rotary disk mixing device, combining said materials on saiddisk and rotating said disk at a relatively high peripheral speed tocause said materials to flow across said disk in a thin lm undersubstantial centriugal force whereby immediate neutralization of thefatty acids is accomplished, removing the mixture of oil and neutralizedacid in a continuous lm into a liquid receiving zone Without forming anemulsion of the oil, continuously passing said oil and neutralized acidthrough said zone, said zone being of such size as compared to the flowof liquid therethrough that there is a partial separation of oil fromneutralized acid, and thereafter continuously centrifugally separatingthe partially separated oil.

5. An improved method for neutralizing the free fatty acids incottonseed oil as claimed in claim 4, in which the charge oil is firstpassed into a mixing zone with a proportion of Water, said oil and waterbeing subjected to a relatively high velocity force on a disk whichattenuates the mixture to a thin film, and immediately hydrates the gumsand resins in the oil, said mixing zone being maintained undersubatmospheric pressure and at a temperature similar to the temperaturein the neutralization step, said lm being maintained until said liquidsreach a liquid receiving zone whereby an emulsion is avoided, andthereafter said Water Washed oil is centrifugally separated to removethe sludge, the passage of the oil through the system being continuousand in a confined stream.

6. A continuous method for refining crude cottonseed oil having arelatively free fatty acid content and entrained resinous matter whichcomprises passing the oil with approximately 1% of water across arelatively high-speed rotating disk in a conned zone maintained undersubatmospheric pressure, in which zone the oil and Water are restrainedto a thin film moving under high velocity, during which movement theresinous matter is hydrated, continuously removing the film of oil andhydrated matter into a liquid receiving zone without the formation of anemulsion, centrifugally separating the resinous matter from the oil,conducting the oil to a second rotating disk, separately conducting aneutralizing agent in substantially the theoretical amount required toneutralize the free fatty acids to said second disk, rotating saidsecond disk to establish a thin film of oil and neutralizing agent underhigh velocity centrifugal movement for a short period, during which therelative thinness of the film, the small amount of neutralizing agentand the uniform dispersion of the neutralizing agent permit apreferential neutralization of the acids Without saponication of the oilor the formation of an emulsion, continuously removing the oil andneutralized acids into a liquid receiving zone without the formation ofan emulsion, passing said oil continuously through said zone at a rateat which some of the neutralized acids settle out, and thereaftercentrifugally separating the balance of the neutralized acids from theoil.

WARD J. BLOOMER. WALTER J. ZAHNISER.

